Centrifugal pumps

ABSTRACT

The invention relates to an impeller for a centrifugal pump permitting the passage of solids through the pump and which maintains a high delivery pressure and capacity in which the impeller has a body having, in cross section, a regular polygonal configuration, an axis of rotation located substantially equidistant the corners of the body, an inlet to the body located at the axis of rotation, an outlet from the body provided in a sidewall of the body and a conduit communicating between the inlet and the outlet.

1% States atent 1 1 1 3,732,932 Daneel 51 May 8, 1973 CENTRIFUGAL PUMPS2,853,019 9/1958 Thornton ..415/213 [75] Inventor: Char Daneel,Wellington FOREIGN PATENTS OR APPLICATIONS public of South Africa I i189,936 6/1937 Switzerland ..415/213 [73] Asslgfleel P" l 330,071 6/1930Great Britain... ,..41s/213 ville, pe Provmce Republlc 574,079 12/1945Great Britain... ...415/213 of South Africa 329,498 6/1958 Switzerland..415/213 [22 Filed: Feb. 16, 1971 Appl. No.: 1 15,333

[52] US. Cl. ..4l6/144, 416/186, 415/213, 415/206 [51] Int. Cl ..F01d5/00 [58] Field of Search ..4l5/106, 104, 204, 415/206, 213; 416/144,500

[56] References Cited UNITED STATES PATENTS 882,478 3/1908 Neumann..4l5/97 495,760 4/1893 Seitz ..4l5/204 882,477 3/1908 Neumann ..4l5/2041,439,365 12/1922 Hazel] ..415/2l3 1,470,607 10/1923 Hazell ..4l6/l44Primary Examinerllenry F. Raduazo Att0rneyStevens, Davis, Miller &Mosher [57] ABSTRACT The invention relates to an impeller for acentrifugal pump permitting the passage of solids through the pump andwhich maintains a high delivery pressure and capacity in which theimpeller has a body having, in cross section, a regular polygonalconfiguration, an axis of rotation located substantially equidistant thecorners of the body, an inlet to the body located at the axis ofrotation, an outlet from the body provided in a sidewall of the body anda conduit communicating between the inlet and the outlet.

6 Claims, 2 Drawing Figures CENTRIFUGAL PUMPS This invention relates tocentrifugal pumps and more I particularly single channel pumps.

Conventional centrifugal pumps provided with an axially disposed passagefeeding into a plurality of passages formed between radially extendingvanes are not suitable for pumping liquids in which is suspended grit orstones. Generally solid matter entrained in the pumped liquid tends toclog at the inlet end to the passages formed between adjacent vanes dueto the fact that at this point the passage between the vanes is narrowerthan the axially disposed passage.

Vaned centrifugal pumps are also not suitable for pumping liquidscontaining long fibrous or stringy material. Such liquids may forinstance be encountered at sewage disposal works. The outer edge of thetrailing vane tends to bite in along the length of the thread as .aresult of which the thread wraps itself around the rotor causing ablockade. Furthermore, a length of rope or rag passing down the axialpassage may be forced into two or more passages between the vanes.

A further disadvantage ofvane type centrifugal pumps is that the passagebetween adjacent vanes tends to increase in cross-sectional area as thedistance from the axis of rotation increases. This decreases thedelivery pressure and capacity of the pump.

Various arrangements have been suggested for overcoming this difficulty.One arrangement provides a stationary impeller with the pump casingrotating about it. This arrangement suffers from the disadvantage thatthe pump is capable only of low pumping capacity and delivery pressure.

In another arrangement aimed at overcoming these disadvantages, animpeller is provided, comprising a single spiral vane which startssubstantially at the point of rotation and completes a single spiral.This arrangement also suffers from a number of disadvantages. Inherentin the structure is an ever-increasing passage width which precludeshigh delivery pressure and capacity. Furthermore, solid materialentrained in the liquid pumped has to travel a greater distance, whencompared with conventional vaned pumps, before it passes out from thearea swept by the spiral vane. As a result, solids passing into thedownstream side of the vane fail to pass from the area swept by the vaneand tend to impinge against the leading face of the vane during thesubsequent revolutions. Not only does this cause wear of the vane, butit introduces additional loads into the system that may damage the vaneand the pump bearings.

An object of the present invention is the provision of an impeller inwhich these disadvantages are at least reduced in their effect.

According to the invention, there is provided an impeller having a bodyof regular polygonal configuration, an axis of rotation locatedequidistant the corners of the body, an inlet to the body located at theaxis of rotation, an outlet from the body provided in a sidewall of thebody and a conduit communicating between the inlet and the outlet.

Further features of the invention provide for the body to bethree-sided, for the sidewalls to be bowed outwardly, for the body to behollow, for the sidewalls to be perforated, in corresponding positionstowards the corners of the body, for the outlet to be located in asidewall between a perforation and the body corner remote from theperforation.

The invention is also directed towards a pump including an impeller asset out in the above consistory clauses.

A preferred form of the invention will now be described with referenceto the accompanying drawings in which:

FIG. 1 is a section through the impeller transverse its axis ofrotation, the impeller being shown in position in a P p;

FIG. 2 is a section through the impeller along its axis of rotation, theimpeller being shown in position in a pump.

The pump comprises a casing l of conventional design. Located inside thepump is an impeller 2 which rotates about axis 3. The impeller is ofhollow construction and may be cast conventionally or pressed out of asuitably rigid metal plate. When viewed in an axial direction, as shownin the accompanying FIG. 1, the impeller has the shape of an isosclestriangle with the sides thereof bowed outwards.

During operation of the pump, the impeller is caused to rotate in thedirection indicated by arrow 4.

The sidewalls of the impeller are perforated at corresponding positions5 which are towards the corners of the impeller. During operation of thepump, these positions are downstream of the nearest impeller corner andin a zone of reduced pressure relative to other positions along thesidewalls of the impeller.

The perforated sidewalls of the impeller allow for the interior of theimpeller to be flooded with the liquid being pumped which in turnassists in balancing the impeller. Additional balancing of the impelleris achieved by weight 6 which is attached to an interior wall of theimpeller. By locating the balancing weight on the interior wall of theimpeller, the weight is not subject to wear in the same way that itwould have been had it been attached to an exterior wall of theimpeller. Furthermore, the weight does not lead to clogging between theimpeller and the pump casing as is often the case with impellersbalanced on an exterior wall. An axial inlet to the impeller is providedat 7 which communicates through conduit 9 with an outlet from theimpeller located at 8. The impeller outlet is provided in a sidewallbetween a perforation and the corner remote from the perforation. FromFIG. 1 it will be noted that the outlet is therefore located downstreamfrom the perforation on the same sidewall.

The conduit 9 is of uniform cross-sectional area throughout its length.Under certain circumstances it may be found to be advantageous todecrease the crosssectional area of the conduit slightly as the distancefrom the axis of rotation increases.

In operation the impeller is rotated in the direction indicated by thearrow 4 and centrifugal forces cause liquid to be drawn from the inlet 7into the conduit 9 and discharged via outlet 8 into the casing 1. Anincrease in the pressure of liquid in the casing 1 causes liquid to beforced into the outlet 10. The comers of the impeller assist in forcingliquid out through outlet 10.

A zone ofrelatively reduced pressure develops behind the corners andthis facilitates flow through outlet 8 from passage 9.

It is believed that there is minimum contact between solid materialspumped and the sides of the impeller, particularly rebound of solidmaterial off the casing onto the impeller is reduced. This results intheimpeller being subject to less wear than would be expected. It hasalso been found that when compared with conventional centrifugal pumps,a higher feed pressure is attained together with an increase in pumpingcapacity. The pump appears to have a decreasing tendency towardsclogging when pumping liquids containing solid material and fibrousmatter than is the case with a conventional centrifugal pump. Lastly,the single vane-type centrifugal pump has a tendency to generate a pulseas the vane extremity passes the pump casing outlet. It will beappreciated that such pulse causes uneven running of the pump which inturn leads .to greater wear on the pump parts. This pulse is notgenerated, to any appreciable intensity, in pumps fitted with impellersaccording to the present invention.

Location of the perforations in a low pressure zone has the effect oflimiting intrusion of dirt and other solid matter into the impellerinterior. Furthermore, should wear of conduit 9 result in a hole beingformed, solid material passing into the impeller interior would beexpelled through the perforations. This has the advantage that theimpeller always retains its balance.

The design of the impeller is such as to reduce the development of eddycurrents in the pump casing. It is believed that this contributestowards a greater pumping efficiency.

Many other forms of the invention exist, each differing in matters ofdetail only. Thus instead of a threesided impeller, four or five sidesmay be provided. The perforations through the sidewalls of the impellermay only be provided along one or two sides.

What I claim as new and desire to secure by Letters Patent is:

l. A pump impeller comprising a body having, in cross section, a regularpolygonal configuration and a hollow interior, an axis of rotationlocated substantially equidistant the comers of the body, an inlet tothe body located at the axis of rotation, a single outlet from the bodyprovided in a sidewall of the body, each sidewall being perforated, incorresponding sidewall positions, towards a comer of the body, meansbalancing the impeller, and a conduit communicating between the inletand the outlet.

2. An impeller as claimed in claim 1 in which the body is three-sided.

3. An impeller as claimed in claim 2 in which the sidewalls of the bodyare bowed outwardly.

4. An impeller as claimed in claim 1 in which the outlet is provided ina sidewall between a perforation through the sidewall and a corner ofthe body remote from the perforation.

5. An impeller as claimed in claim 4 in which the outlet is locatedcloser to the perforation than the corner remote from the perforation.

6. An impeller as claimed in claim 1 in which the impeller is balancedinternally.

1. A pump impeller comprising a body having, in cross section, a regularpolygonal configuration and a hollow interior, an axis of rotationlocated substantially equidistant the corners of the body, an inlet tothe body located at the axis of rotation, a single outlet from the bodyprovided in a sidewall of the body, each sidewall being perforated, incorresponding sidewall positions, towards a corner of the body, meansbalancing the impeller, and a conduit communicating between the inletand the outlet.
 2. An impeller as claimed in claim 1 in which the bodyis three-sided.
 3. An impeller as claimed in claim 2 in which thesidewalls of the body are bowed outwardly.
 4. An impeller as claimed inclaim 1 in which the outlet is provided in a sidewall between aperforation through the sidewall and a corner of the body remote fromthe perforation.
 5. An impeller as claimed in claim 4 in which theoutlet is located closer to the perforation than the corner remote fromthe perforation.
 6. An impeller as claimed in claim 1 in which theimpeller is balanced internally.